Snubber



Dec. 30, 1930. P. N. PEERS 1,787,282

SNUBBER Filed March 1, 192s d Patented Dec. 30,1930

PATEN Tl oFFi-CE 'PETER NIcHoLAsPETEns, or BROQK'LYN, NEW YORK SNUBBER Appiieationmea March 1,

My `invention relates to motion vcontrolling devices and, more particularly, to devices of f this character for ,checking the recoil of a y springZ connectionbetween elements of a mechanism.

. y Devices ofthellatter class, when usedl on spring, suspendedr vehicles, are commonly -knownas shock absorbers.V In theso calledl Vonefway i shockV absorbers, or snubbers,

' 151 the springs themselves are depended upon to absorb the shocks suffered by a vehicle mov- Y Y -ing over an uneven, road, the function of the shock absorber being that-of retarding the recoil from .the compression ofthe spring.

" VThe present invention is concerned with snub- '25 facturers claim thatiin theirffsnubber the fcounteractingspring Vhas Vno other function than that of rewinding the band,.buty this contention clearlyl` involves av fallacy. It VVtakesas much energy'to rewind a band on a 3o drum as it takes to unwind it, assumingequal' f resistancein both cases. the counteracting Y @spring were of small power, a correspondvingly highfvfrictional Yresistance between the drum andthe band wo'uldibe necessaryt'o ef-y s'vfect the desired snubbingY action, but, in rewinding the ,bandon the drum, the same frictional resistancewouldhave to be overcome,

Y and this could not be accomplished by a rewinding spring of small power.. Thus, the

lo `assumption of a low power counteracting f` l `spring leads t'o' obviously contradictory conl clusions. e .The power ofthe rewmding spring, whilenot necessarily of the same order as the powerjof the spring therecoil of which the 1 3 .as device is intendedto snub, must be substantial andas matterofffact, commensurate f-I'f'N-v-,h' the 'power .of'ithe opposing spring, and,

Y if it issubstantial,thenthe'rewinding spring isboundto functionasia 'counteracting spring 5o also, opposing the-recoil movement. There 1928. serial No. 258,316.

is a certain interdependence between kthe counteracting spring and the frictionalresistance in these devices which sets definite limits on both. The frictional resistance can not be made'arbitrarily high, nor the' tension 55 of the counteracting spring arbitrarily low. Unless the counteracting spring is of considerable power, the device will not be operative.

y The counteracting spring, therefore, is a controlling factor 1n the operation of the con- 60 ventional drum and band type of snubber, claims to the contrary notwithstanding.

The novelty of the present inventionresides yin the fact that no additional force, such, for instance, as the tension lof a counter- 4acting spring, is introduced to4 control the snubbing action. Frictional resistance to motion is stilla factor, but the device operates on the principle of causing the force of the v recoilV itself to control the'snubbing action. 70 The force of therecoil is the force whichactuates vthe device and, as such, it is a self-controlling force.

Theadvantages which it is the purpose of this invention to secure are numerous. In the first place, the invention is independent of the somewhat contradictory theoriesprevailing today as to when the resistance developed by asnubber should: be maximumv and whenthis resistance lshould be minimum.' so

jSome engineers believe that the resistance should be maximum atthe beginning' of the recoil movement and gradually decrease as thismovement proceeds; others areof the opinion that the'reverse condition should pre- 85 vail, i. e.,'that the resistance shouldl be minimum at the inception of the "recoil, gradually increasing to a maximum as they recoil movementr approaches its end;'otliers, again, adhere tothe idea that the resistance should be constantthrou'ghout the recoil movement; and some engineers have adopted the theory that the resistance shouldincrease from the start of the recoil movement up to some intermediate stage vand then decrease again, lwhile 95 others claim that it. should beginy with afdecrease and end with an increase. In the present invention, all of these conditions and-,in fact, any conceivable set of conditions as toy the lmanner in which the restraint shoul'dde- 100 velop may be satisedbyiadopting a suitable shapeffor the revolving' drum which constitutes yone of theop'eratingelements. of the dev vice, Without inany manner departing from 5 the; broad principle,underlyingits operation, l as this-principle has been stated in the pre- 'ceding paragraph. f

Anotheradvantage which it is the'purpose`V tent of frictionalcontact between the'drum andthe bandy is constant during the snubbiiig" operation.y lRegulationoffrictional'resistance Y gis provided by the simple means ofv enlarging.

.` ltact. -YA-nimportantreature of this .regulaf KVorfreducing'the extent-of the fri'ctional con- 'jtion -is that'y the recoil .movement Vis automatically-arrested before'it can become excessive.

--Additional 'means vfor regulating. the snub" ;;bing effectis provided in thattheposition of Y K Vthe fulcrum vabout -Which thefo'rce of recoil.

exerts its" self-restraining action may Vbe:Y

varied5 as; for instance, in the preferred form .f ofthe invention,bychanging the eccentricity.

.the sniibbing eii'ect lmay 'beiregulatedg by .the ..5 lcombination' of the `.above .mentioned -ineans .results inahigh: degree of adaptability to a variety .of conditions and abroadness of ap` l .p1/It is alsov the `purpose of this inventionto eliminate the undesirable and` troublesome feature of preloadingvcharacteristic of 'all ing spring inthe present :invention, and the 7 force of recoil is the controlling factorinthe operation of the deviceyjpreloading, in ti e4 accepted meaning of theteri'n, does not exist iV inthe present case'. A lt is true that the .illus- V '-,tration reproduce'dinY the dra-Wings shows a"` spr-ingfor causingv thedrum to revolve, but.V the `functionof this spring ismerely that of` l vturning the drum to a'fpositionivhere it re--.

tains-its close contact With' the friction band,`Y

[so asto take upthe slacljof thelatter'. :In so far".'as'ithensnubbing action of the Vdevice. isy

. concerned, this spring may be entirelydisre- V,55 garded. Indeed, once -.the`` drum hasbeen from-thejdrum'. ASuch an arrangementis, ofl

--course,. feasible and, if it isnoty adopted here, itis because it Wouldintroduce complications Vfor'vvhich'there is nojustiiricationin View of ...the negligibleefleotof-the spring on the f-snubbing action of ythedevice. Besides, the

, l v manner of taking up the slack of the friction j-` fHi 7.1101 Palit #of the present invention.Y

is ya .cylinder 'of circular 'cross section, the 'eX- bron ht back into close 'contact vwith the fricf It need not ber-ofV the spring type.. -llfany vother standard Ways'of accomplishing Vthe sameresult could be adopted.. For'instance, the positionofthe device might bereversed inthe illustration shown herein, i. e. the

terminals of the friction band' could be se cured'to the-bodyA, and the ,rdrum mounted on Athe body 'B,-infivhichcase the drum would assumethe right 'pesiticn under the action of gravity, 'vv'.itliout any, spring at all. VThe vspring for 'taking up 'the slack ofthe band y lhas been selected'here for the purpose of illustration mainly because` of its simplicity.

k lt doesfnothave to be powerful, like the counteracting spring in the conventional drum and band type ofsnubber. All ithas todo is to turn .theJdruin vWhen there is practicallyno resistance-to suchgturningbeyond the small Weight'of. the drum itself', anda. coinpa'rativelyvvealrspring Will amply serve the purpose. .The conditions are Vvastly",.different from those obtaining in'snubbers vvithV counteractiing springs rWhere thev revvinding voperation k'must'overcome a very high fretinarreslsn ance/'fj'.

.. Evenfshould oneconsiderthetension of the Y slacheliininatinofs rin inthe resent case 'Y v asa form of'pi'eloading at least, ity caribe saidV i a 1 'L forit that it is aininimum ofpreloading and of the drum. :The Wide range Within Which-V tha't it .is independent of `load v variations.

For instance,in the casek of a spring 'suspended vehicle, a light load ,meansra stiiierve- "hicle spring, and` aheavyjload a softervehicle spring. .In accordance'therewith,when

the snubbery is controlledbyl a xcounteracting L spring, rthe preloading varies, and, usually,

lOl)

Vadjustments areI necessary to vbringthe pre the load. ln the 'present invention, if one Werevto call the sl'ackeliininating spring a form of, preloa'ding, iwhatever '.prel,oadingV there' may be would remain unaffected Abyjva- Q vvith noipossibility ofinitial slippage, even at ,times of. unusually-.strong or sudden-recoil movements: 'r Suchinitial'slippageiis not un'-v yiisual in snubbers'of the conventional drum :andband type (stationarydrum,vband windz ling andiinvvindingcnthe drum) .f Even the flexible band is; not I actually `slack immediately preceding the.recoihinovemenh itis never fully stretched,and theintervaloftiine loading factorin line Avvith the: variations in K iis duriiig 4'which it'iindergoeslr'the stretching l.process Within` the limits ofitsfelafstic'ity, under the-action Y necessarily accompanied bysoine slippage loir .the Edrum, because durinfoA #this intervalfthe contact friction` betweendrum isY not Vconiplete t present invention, the. band Vis linstantly ythe ltractive, force, is

.pressed onto the druniat the;,.v'eryfV inception iof thel recoil movement, vWith-.fthe-ffiill force ne band' andthe Yloped.. .A 11.11 be fof the recoil andunder a .maximum of' tension, before thevdrumgisV caused torotate, so

that no slippagecan take place.

vention vwill yserve similar niecl. aiiisnis ot va-,

Alo

.A nother benefit r'tobe 'derived from the present invention is easystandardization. A snubber built in accordance with this iuwhich must correspondto the load on the ve- :,hiclev spriiigLhavegto be designed'to accord with thesize and weight ofthe vehicle.,

. It is also tliepurpose of the present inven- VAtion to extend the 'life of the snubber by reducing' the main cause oit'k wearv therein. y,Th

above Amentionedregulation ot' the trictional resistancejpermits one to obtain the desired snubbing eiicect: with comparatively little friction between lthe drum andthe band. VAbility to use a low coefficient of Jfriction Vfurther means that the device` can be operated in lubricated condition. thus assuringI y not onlyr long life, but smooth action. l The slow, normal wear isfautoniatically taken rcare of by a slight advance in the counter in thecoiirse of'th tion which 4follows.

en v

clockwise vrotationl .of the drum impelled by the slack eliminating spring. i `v f To 'the various purposes and advantages briefly enumerated above may be'A added the y lextraordinary vsimplicity of the device and its obviously low" cost manufacture. n Some -y of these .kpurposeswill 'be further discussed L.description of the `inveii-v In vthe drawings' Figures l, 2 andr S 'are froiit'views of the preferred form of my iii-Y vc'ntion, at three ditler'eiit stages oi. its operation. Figure iis' a `top view of the same device wh'eiiiin the position shown inv Figure l. Figures' 5 and Gare i-iont views ot this device when yprovidedY*withv means 'for varyvlino'tlie arc of contact betweenthe drum and `thedbaiidgFigure Afi;is'aside view ot .the drumpar'tof the device showing a' double windingaof the Vbauch-as another means ttor increasing"v the are of contact. Figure l8 is a front view ofa modilied'form of the drum,

f3 inv that it lia-sbearings for' the axle lonwhicli the drum rotates at viV/ariousdistances `troni the central; axis thereof. Figures@ lO, and

l1 :are front drums.. Figure'l is a partial cross sectional view o tadetail in the arrangement ofthe l drum ai f tion tof-:ti idevice'iii so far astheynieansor securingltlie end"k of theiband is concerned.V

lrbandf'Figure ,i3 is a modifica# "7 vrFigure 14v isschematic .iiew `of `the in- I veiition as 'applied tov aspri hicle. Y Figure '15 is al diagram illustrating thetheory of the device.

g suspended ve-v Referring to the drawings in detail, 1 is a bracket attached to a body A, which may be the frame oit' a spring suspended vehicle (Fig. 14). A cylindrical drum 2, of circular cross section, provided with a suitable groove 3 alonv` its. periphery for the admissionof a flexible member 4, 4, which may be a friction band, a` cord, or the like, is eccentrically mountedv on the bracket l for rotation about the axle 5. As shown, the axle is fixed to the ,.75

bracket 1,'but, of course, the axle may be iixedl to the drum and rotate in bearings provided therefor on the bracket. A spring 6, coiled around-a sleeve 7 in such a manner as to keep 2 or-:the arms of the bracket l., is anchored i' at oneend, 8, in the axle 5, and attached, at the other end, 9, tothe drum. For 1the purpose of illustration,-thespring 6- is shown y the coil from being fouled by either the druinexposed, because of the simplified drawingas in practice, l prefer to make the drum hollow, affording space within to accommodate the spring'. The flexible member 4, 4, has its l terminals secured iii any suitable manner to a ksecond body, B, which may be an axle oi the@ `vehicle having' the frame A. ln the drawings, the flexible member 4, 4', may be considei'ed ashaving two ends rmly attached 'to the body B and joined together at 10. Itis not essential that the two ends or" the flexible member be attached to the' body B jointly. In Figure i3 is shown a modification wherein each end portion of the flexible member is separately secured to the body B, one at B, andthe otherv at B, by means of separate clamps l() and 10. A stop, in the form of a crossbar ll on the bracket l, serves to limit the rotation of the drum 2 counter clockwise, the limiting. position of the drum being indicated iii dotted lines on Figure l.

' ln Figures 5 and 6, the device is shown provided with'means'` for varying the arc of contact between the drum 2 and the friction band 4, 4tlie clamp 12, in one case (Fig. 5), serving to increase vthelength oi" this arc, while the separating member 13, in the other case (Fig. 6) elfects a reduction iii the length of the' arc. Both devices are adj estable, as, for instance, by moving the clamps up or down. The variation in the length of the arc `of contacty between the drumv and the band y dieriiig virom the drum in Figures l, 2 and changes the frictional resistance to rotation the drum. Another manner ot' increasing this frictioiial resistance is shown in Figure 7,

'v'.lfhedrum may be so designed as to permit variation inthe degree of eccentricity. @ne

way of accomplishing this is shown in Figure 8, wherein aseries of bearings (5', 5, 5',- for the axle 5 is provided,.each bear-ing being dis- V posed ata dilereiit distance fromthe periph! acteristic" positions 'duringrv the operation of the device -areshown in the diagrammatic Q'm'Figure 15,1.vlfi'erein the central axis of the eryofthe-drum. By selecting one or another of these bearings for'the aXle 5,' the eccen? tricity. ofthe drum'may be increased or 'dinfiinishedv f Only three bearingsvare shown,

but, Iobviously, theirn-umber maybe increased. Y The druinis, in eect,` `a cam pivotally mounted` on thebodyii.V Alts-charlruin, indicated'by the lletter C, has been as- Y ysumed las stationary, andthe pivotal aXis as e rotating relativelyto the central aXis,'dif`er f entpositions of the pivotal axis being ,indicatedby' 0, O', O". vThis*diagram illustrates konly the relative positions of the :cen- Y tra'l andthe pivotalaxes of the drum. lt'is,

' therefore, immaterial v which one Vof "them is i assumed as stationary, andwliich one as rotatingv. The total angle'of relative rotation "in the'V course of normal-operation is indicated in Figurelvr by the letter a.

Vat the two ends of the-flexible member 4, 4f,

The pull 'is not exactly'jthe'same for certain positions ofthe drum, but the difference is slight, and

vr'we may VVasfsuineffor the purpose of the folf lowing f discussion, that it is exerted with b equal force at yboth ends throughout the opervariesrroinvm'to 00, and, ontheother '..moment of the operation I Y K' vit willbe seen' that atorqueT-:Pp is'applied. tothe drum on one side, tending to rotate ity anticlockwise, anda-torque T =Pp on theY i' ationofthedevice.

' lone 'side i The` pull is denoted in Figure 15 by l. ltis applied to the drum,.on

atthefend of a lever arm whichr side, attheend of a lever armvarying from t0 ,yl/(f/ v *Denoting by .p the length of the lever arm on one side of the drumat any ,Y l and-hyp the lengthof the leverl on the" 4,0., Y e

other side, Ytending toy 'rotate it clockwise. j The net result lis a differential torque Y i 501m the-:clockwise direction;` lt i'sclearfrom i the. diagram, Figure A15,'tliat thefdifferen'ce v`-g9"-Q9 atlirst increases, as the pivotal airis from the position@ to thepositionfO,

encepp may be made toY follow a different law'llhus, Figure -9,.= the cam Vshaped. drumisjfornfiedsolas tofmake 20 andjpy conl, after which tliedilfeieiice v 'i 1,787,282 l stant within'the normal range of rotationV of the cam. In Figure l0, p is constant,

Vwhile p steadily increaseswitliin the Vnormal range` of `operation (for'the counter `cloclr- Y wise rotation of the cani) and in Figure V1l, p still being constant, p steadily increases whenthe cam rotates Clockwise.' .Clearly the v shapelof the canrmay lbeformed so as tosatisfy vany manner of ycl'iaiige imposed on the difference of the two leverarms j? and 1p',

rllie relative values Vofthe two lever armshave an importantbearing on the operation of t-heV device, as will becomeclear.when` this operation is explained. .Y Y A v lln Figure 12, a frictionfmemberl4 is interposed between the drum 2 and thetlexible member 4,14', with a protective strip 15,;preferably of steel, vbetween theflexible memberk 4, 4', and the friction member 14;"the eXible member, the` protectivestrip, andv thefriction member being secured together, as, for

instance, by rivets 16. l/Vhileia rectangular Y l groove is shown in the drawing-,'it is obvious thattheshape of the groove may be dierent,

and that itsV surface Vmay `havel .various fricv 'tional coeliicients when in contact .with the flexible member o r with the friction member 14.

In Figure 14, A is aportion of the'iframe of a spring suspendedfvehicle, Ba wheel axle, and S a spring connection between the axle-Band the portion A oftheframe,

" To illustrate fthefoperation'of the device,

this operation V will A be explained las' Vapplied to a' spring suspended vehicle, 'with especial `reference to Figures; 1,2,8 landIj-14.v

Whenv the vehicle encountersan A.irregularity in its even path, the wheelaxle lu will be thrust` upwards, compressing the spring VVS and, at the'same time, causing theV flexible 'member 4,' 4', toloosen'iits grip onV the drum ,2. The slack of the flexible member 4, 4', is

immediately taken upy by' the;V action ofthe drinn 2 whicli,i'mpellediby thespring 6 vtoV turn (fanticlockwise, in V:the illustration), closely follows vjthe 4displacement of the contact therewith.y A comparatively Y weak spring may be usedffor thus taking upy the slack ofthe `flexible niemberf'4,'45.e r#The position ofthe several parts ofthedevice at the moment when the thrust isapplied'tovthe aXleB is illustrated in. Figurefl. IDuring the first stage of'operationgthe.snubb'er will gradually pass freiny the position shown -in Figurel to j that Villustratedfin-Figure 2. Y VVVllienf in the latter position, f ity is at Ytliefendl of thefirst stage,'and the movement 'ofrecoil flexible member, 1 nf'iaintainingl itsufrictionalj f commences.'v 'ln passing,frenigat-lie position inl Figure lto that 'Yin-Figure 2,'thefdruin 2, @turninganticloclwise, hasidesc'ribed an an'- gle commensurate V,with thel movement of the axlev VB relatively to the l frame A ofthe vehicle" and, therefore, commensurate' withY the amplitude of thefoscillationofthe spring S, i

device".

greater` will' b 'efftheamplitude `of the oscillation'andthe greater the 'angle described bythe drum;A As soonl as therecoil movementV commences, the downward pull of the force foffrecoil, transmitted to the/drum through the flexible member 4, 4', rwill'apply'the opposite-torques TandT thereto, which ac- .tion,`as already explained, results in a net f ing to rotatefthe drum clockwise. Since therv flexible member 4, 4",has fixedfterminals, ity `can' not turnV with the drum@ Therefore', in

i5 Y a,

.rotating,the drunifmust overcome the fricdiderential torque TT- T, or 'P (20 79) tendtional resistance along its arc'of contactwith theflexible ',inem'ber.` The greater the lengtho'fth'e arc'of contact,the greaterfis Ythe braking eect onthedrum.

opposite "effects thereon,l the flexible' member`4,`4, takes itsl gripjon the drum instantly andlunder full tension,/i. e. the full gripof theflexible member on the drum necessarily precedes the "clockwise rotation ofthe drum,

sothatnoinitial slippage occurs, which' can not be saidfto'V beVV thev case with l other snubbers ofthe saine type, as was pointed out.

y ,Thei'differential torque considered *in the precedingdisciission is the torque resulting directly from the pull'exerted on the drum by the force of recoil. To'this torqu'efinust` be'fadded that originating in the tension of drum. From'themathematicalftheory of the device, the following expression of the final ,i dierential torque'. AT disk obtained 40, q

. Medef-Fair where F is the force of recoil;l l' contact between thefilexible member and the y drum, in radians; 7c the rcoefiicientof friction .45, i

1 and CA a between 'the drum ,and the flexible member;

and..l qu

y i The smaiier is mediadatenfefqiie xr, 4thegreater kis the snubbing effect, and vice mounted drum 'of circular cross sectioii,illus [tratedvin Figures l to 3, the ratio of to p increases froin the inception ofthe recoil movementuntil-v the mechanism passes throughl'its (p fthe `Farc of constantinvolving the values of V7cnormal state (illustrated in Figure l), after which it decreases until the forcelof the re P co'ilwill have spent itself. The latter condition may be reached without departing far from thenormal position, if the dampingV effect of the snubbing action is sufliciently strong. Accordingly, the difference p pew, and with it the differential torque AT, will at Vfirst increase, if the difference ppe"1" iiif y creases at a more rapid rate than the rate of decrease of F, until vthe normal position is reached, whereupon the differential torque AT-will rapidlydecrease, because both of its variable factors are then decreasing. If, on the'other hand, the `decrease ofthe forceF is more rapid than the increase of pf -pe" ",V

the differential torque AT will steadily decrease, at first slowly, then rapidly. I prefer to so construct the device that the first one Y of the two alternatives mentioned above will n @wingto the fact that'the force'of recoilv l isapp'liedto the drum at points where it has'y thek condition most desired by manufacturers of motor cars. However, itis not my intention either to' limit myself to satisfying the last mentioned condition, or 'even to insistv on'its preference, asthe device is equally adapted to' satisfying entire'lyother conditions; p Y v l --lf itlisfdesired to modifythe manner in whichfthe diiferentialtorque AT progresses 'with the 4n'covement of recoil, a cam of suitn 'afable shape maybe substituted for the eccenthe frictionalresistance to rotationofthe` trically mounted drum of circular cross Vsection, the changes inthe differential torquev following the changesof the lever arms p and'` p as the cam rotates. The-latter changes in the cases of the several cams shown in Figures 9, 10 and'll, have been previously discussed, and it is not necessaryto follow'the Subj ect further in order to perceive'the characteroftiese Vand similar modifications of the'device, or/how they adect theoperation of the snubber'.` It is to beunderstood, however, that the specific shapes shown inthe drawings are merely illustrative.`

'It will be noted that the variation between the highest and the lowest values of the ratio pto'p will be more or less pronounced. according asthe angle a (normal range of rotation of the drum) is greater or smaller. There is, however, a value of this ratio for which the differential torque AT vanishes, viz. when p is equal to fick", asy the above given formula shows, and when this Y minimum valueof the ratio of p to p isfreached on the recoil movement, the device rbecomes teinporarily locked, and the recoil movement is Vautomatically arrested until the vforce of recoil will have spent itself and a revers'alof the relative movement of the bodies A and Breleasesithe loclr. Thusfatimely stop-is pro- .l laY Y .,drum. `However, as an additional precau-lV 'trom-I may include a stop to the anticlockwi'se .rotation-fofthe drum in thepresent device.

v 20 SuchV a stop, in the vforinof a cross bar ll on vii-.lede which effectively -,prevents. theY y recoil movementfrom becomingexcessive.A j

Means must be` providedto prevent' the drum vfrom reaching Va .position for; vwhich the `ratio Vof p to p'attains'the above-mentioned, minimum value during its anticlockwiserotai-VV tion under theaction of the slack eliminating Y spring 6, when the upward thrust is vappliedA to the body B', otherwise the device would be- -come locked before it had a chance to'oper- K fate.' A Such a means is always supplied, in the caseof; spring suspended' vehicles, by are` silient stop V.either on the 'spring itself,`uor on the frame which prevents an excessivecoinpression ofthe spring-and, therefore, an uri-- due :angle of anticlockwise rotation ofthe the bracket 1,;is shown in vFigures 1 and 4,

j theflimiting `position of. the vdrum:beingindicatedin dottedlinesjin'Figure-l.-

It maybe remarled ,-in passing, that the* t 5f valueofthe ratio of pto p. for which'the def,V

Vice' becomes locked is attained before the drum can :reach a dead center' position either onthedirect, orvonthe recoil movement.

The ymethodrof .controlling the friction'alg resi-stance betweenuthe drum .and thegflexible 'p member is extremely simple.' Ity Yconsists in varying theV extent of the Vfrictional vcontact between them; Asis clear from theconstruclv tion, inthe case ofthe eccentrically mounted cylindrical drumof circular cross section, the n .arc.ofconta'ctbetween the flexible memberV andthe drum islconstant throughout the,

,l operationl" rl`his constant arc of contact may be made larger Yor smaller, thus modifying the frictional; resistance Vwithout changing lthe frictional coeflicient. l However, I do not,rv meanl to 4restrict myself to this particular" method of changing .the frictionalr resistance, nor -to exclude changes of form or material of vthe groove inl which the flexible member rests, or variations ofthe frictional .coefti-j ycient. The method of varyingthe frictional resistance'by lengtheningor shortening the arcjrof contact is, however, so simple as tov commend itself 1n particular. Means for doing s o are-shown' in Figures 5 and 6, a movef ment up or'down of the clamps'kl2 or '13 affording la wide rangeof variation. t

j Additional means-,for regulating the snubbing Aaction is afforded by the possibility 'of varying the eccentricityv of the drum. In

FigureS a drum is shown withseveralbearings for the axle on which the drumis mounted ffor rotation, each at a different distance from thev central axis of the drum. The

closerithebearing is to this central axis, thev smaller is the eccentricityofthe drum, and'v y the'smaller, also, the: ratio. of the lever'arms p "and p; ."'I'lowvv changesV in this ratio `atleet thedierential torque AT and, through thisv ms'zgsa produced` by variations ingthe eccentricity of the drum2 maybe effected with any other cam by a suitableichang'e in thepositionfof its pivots.

The combination ofwt-he above .'described i doublemeans of regulationmakes itpossible to meet almost any imposed conditionsas to the lmanner in which the snubbing effect should develop. Foronething,thedevelopment may be caused to be rapid, or gradual.1

For another, it readily adapts itself to'lurbrifn eating conditions, i. e. toconditions-under which the vfrictional coetlicient Vis yerytvlow, because, no matterhow lowfthis coetlicient may be, itis always possible to so "select the eccentricityl ofthe drum and theflengthfof the arcv off'contact betweenthe drum and the iiexible member as to lobtain a differential troque'AT of the` requisite value for produc-V l ing the desired snubbingjefecti.'lhat the manner in whichthe snubbingietfect develops `may be made toa'ccord with 'any preconceived theory has alreadybeen explained. .l Tomeet any imposed condition, j itis; only necessary tweenz thecam and theflexible member, the angleof normalfrotat-ionof the cam.,VV The to properlyselectthe various jfa'ctorsfentering into l`the operation "of the devices-such v as the shape o f the cam, `the position* of Yits hpivots,-thelength.ofthe arc ofcontact be-v 100 possibility of operating the .device under lu- Y bricating conditions vis importanti inasmuch as the life of the device isextendedthereby.

The wear in snubbersjofthe ltype here considered willjnaturally showitself mainly in the frictionelements, il e. the drum andthe flexible-member; )In devices which depend on a'counteracting spring for their operation,Y normal -wear' ls'talen care of by adjustment of 'the'. count'eractirrg` spring or by otherwise tighteningthe flexible member. It isia ,featureofthefpresent linvention that normal wear of the operating'partsisautomatically takenfca're of byv theself adjustment of the drum in vseeking Vits proper position Vunder the action of the spring 6 when, owing to any normal wear of. the friction elements,

the slackvof the flexible member is slightly increased.v` To provide for vmore extensive wear, a separate andV easily replaceable friction member lll anda protective strip 1.5

may be added, as illustrated inlfigure 12. -V It' has been stated hereinbefore thatFigures-1,2and 3 illustrate three characteristic kpositions of the device at `the commencementor at the termination of definite stages of operation. It should be remembered, how*-Y ever, that under normal conditions therecoil ihsaasa willnot extend Aasisindicated'by the lposition ofthe drum iii 3. Ordinarily the position of the drum at the termination of Athe recoil movement will be somewhere between that showniii FigureV l and' that illustrated in Figure -3,the oscillation of the spring S (continuing the illustration as ap-y vpliedto a spring suspended vehicle) being 20v' the normal Vrange ot rotation of the drum, de-

noted. in the drawings by the letter al.. mayv Ydamped bythe snubbiiig edectl ofthe device. On the otherhand, the position of theV drum, in p its normal state, ki. e. 'when kthe be taken aslying between the extreme limits indicated in Figures and13.

IclainijfA s Y 1 l. In combination vwithtwo relativelymovable' bodies subjecttofthe interaction orp a .ioice, a.A member movably connected to one ofsaid bodies, means made operative bythe y 3o l'eletivemotion ofsaidfbodies in one direction for causing said force to beV appliedto said member 'at vpoints where ,the actionsr of saidV forceon said member are opposing one another andsettiiigsaid member in motion in differential response to the opposing actions of'said force, and means Vtor restrainc ing the 'motion of said member.

@.Iii' coinbiiiatin with two bodies having` a resilient connection adaptedv to kcause a recoil when said bodies are vmoved relatively 'cotonek another, a member inovably connected to ,one of said bodies, means made operative iy'the relativemotion ot said bodies in one y tion for causing the force of saidA recoilto be yapplied to said member at points where the actions of said force-on said member are opposing onezfanother .and setting said member in reverse motion inditlerential response to the opposing actions of said force, and meansl Ytor restraining said reverse motion.

3. In aidevice for damping relative oscillation oiC two spring connected elements of a inecli'anism, a movable member on one `of said elements, means made operative by a swing ot said oscillation -ior causing said member to move to an extent commensurate with the amplitude of saidsv-Jing, and means made operative by the recoil from said swing for causing thefforce of said recoil to be applied tojsai'd member atY points Where vthe actions of said force onl said member are opposingone another, theopposing actionsof said force being-diiV deiiniteA relation' to the extent et the motion of said member.

Ll. In combination with two relatively movable bodies subjectto the interaction of a yIorce, a member rotatably mounted on one oi'said bodies, means made operative by the relative motion oi' said bodies in one directionr'or causing said force to be appliedto said'memberl at points where it is adapted to produce opposing torques thereon and setting said memberr inrotation in diilereiitial resnonseto said ooiiosinfT tort ues and meansl .L .L i c 9 for restrainingthe rotationoic said member.

In combination'with two bodies having aresilient connectioi'r adapted to cause a recoil when said bodies aremoved relatively to one another, a member mounted for rota-v tion on one of said bodies, means made operativev by the relative motion ot said bodies in one directionior causing saidffmember to rotate, means made operative bythe recoil from vthe' relative motion of said bodies inY saiildircction for causing the :torce of said recoil to be applied to said member at points where it Vis adapted to produce opposing torques thereon and setting said memberin reverse rotation iii diilereiitial response to straii'iing said reverse rotation.

6. In a device forl damping relative oscillationoi two spring connecte-d elements of aadaptedy to produce opposing torques there-y on' in ydefinite relation to said angle.

f 7 In combination with two relatively movable bodies subject to the interaction of a force, a cam shaped member pivotally mounted onone of said bodies, flexible means made operative by the relative motion of said bodies in one direction for causing said force to be applied to said cani shaped member at points where it is adapted to produce opposing torques thereon and setting said cani shaped member in rotation in diiterential respense to said opposing toi'ques, and means for restraining the rotation of said cam shaped member.

8. In combination with two relatively movable bodies subject to the interaction of a force, a cylindrical drum eccentrically pivoted onone of said bodies, means made operative by the relative motion of said bodies in one direction for causing said torce to be applied to said drum at points where it is adaptedto produce opposingtor'ques thereonl and said opposing torques, andmeans for ree 9.. yIn combination-with two bodies having a resilient connection'adaptedto cause a remade operative by the recoil Jfrom therela tive motion` of said bodies in said-'direction for causing the force of said recoil to be appliedv to said cam shaped member points l where it is adapted to produceopposing torqiies thereon and setting said cani shaped member injreverserotation in diierentialresponseto'saidopposingtorqnes, and means avresilienticonnection adapted to causea re- '20v coil when saidbodies are moved relatively to for restrainingsaid reverse rotation..

10. In lcombination with two bodies having *one another, a cylindrical drum eccentrically pivoted on one oisaidbodies, Aineaiisinade :operative bythe relative motion oi saidv bodiesy in onev direction for causing said drinn insaid direction for causing the force of said recoil to be applied to; said drum at points where it is adapted to-prodiice opposing torques thereony and'setting said drinn in reverse rota-tion inv-differential response to said opposing torques, andmeans for restraining Y said reverse rotation.

' 11. Ina device for damping'ielativefossil#` lation 'o two spring kconnected elements of a mechanism,a cam shaped member pivotally'mounted ono-ne of said elements,y means made operative by a swing ofsa'id Voscillation ffor causing said cam v shaped member Vto rotate. to an anglecoinmensurate with the! amplitude ofsaidswing, and vflexible meansY .ma'de-operativeby the recoilfroin said swing .orcausing the force ofvsai'd recoil. to befapplied to said' camshaped niembenat points where "it isA adapted to yproduce 'oppos'ing -torques'gthereon Viii vdefinite relationto said angle. 'l

12; In a devicer'for damping relative oscilv lation oic two spring connected elements of 'a mechanism, al cylindrical drum eccentrically pivoted on one of said elements, vmeans made operative by a swing of said oscillation for causing said drum to rotate to an angle f commensurate with theia'mplitude oi' said swing, and means made operative by the recoil from said-swing for causing the Jforce of said recoil tobe applied to said drum -at points where it is adaptedto produce oppos- Y ing torques thereon and prodncea dideren-V tial Atorque in' definite relation to saidangle; l3.- in combinationl with two relatively i "movable,rigidbodiessiibject-to the interaction of arforce,f.a member movably connected toone of saidbodies, and' means originating and yterminating in the'other one of said Imerese f f bodies for f tr'ansinitting'j said vforceV to, saidl memberat pointsY- where theactions ofsaid force onfsaid memberfare opposingoiie another. Y f 1 '14. In combin'ationwith'- two resiliently connected rigid bodies, a member 'inovably connectedfto one'of saidvbo'dies, and means originating and 'terminating in tliel other one of said bodies for transmittingfthe yresilient action between said bodies to said member at. points where the force oi-recoil from said member in opresilient action acts uponsaid posing directions; 'f In V`combination with 'two relatively ymovable bodiesunder Vthey action oi aiorce, a

member rotatably inoiinted on one. oi said'boL` ies, and means originatingand terminating mounted for Arotation on lone oils'aid bodies,

p and connecting kmeans to saidfc'ani shaped torotate, means made operative by the rey coilfromthe relative motion of said bodies member originating and terminating-,in the ot i the rotation of said camsliaped member.

*17. lin' combination withfrtw'o' relatively her one of said Vbodies,:responsiveto there# ieg .iovable bodies subject toy theginteraction oi" a force, a cyiinorical drum eccentricaliy pivoted on 'oneof said'bodies, an'dconiiecti'ng means tosai'd driim originating and terminating in the other one-of said bodies, re-

sponsive to the relative metion of said bodies,` ior c iis-ing said orceto control the rotation .of said drum,

1 8; in combination with two spring connected elements of amechanism, a cylindrical ydrumgeccentrically pivoted onV one ofsaid eleineiitaand connecting `means' yto said drum originating and terminating in ythe other one of said elements, responsive tothe action oi said spring, for causing the force of vrecoil therefrom to ontrol the rotationof .said drum.Y

19'. In @combination k'with ,two relatively movable bodies subject `'to the interaction of aiorce, a member 'movably attachedy to one of said bodies, and connectiiigmeans originatingan'd terniinating'in the other one of said bovdiesradapted to have a V res'ili'eifit gripl on said member when the relative motion of said bodies is Vin one direction for causing said force to move said member against said resilient grip,

20. In combination with Ytwo :relatively movable bodies subject `to the interactionoi' a force, a niemberrotatably mountedon one of said bodies, andconnecting,meansorigi nating and terminatingV in tliefother one of said bodies adapted to have a rictional grip on said member -whe'ntlie' relative motion Voi" said bodies is inV one direetion'for causing iis Y Said tormenta-te seid. member against Seid.

frietional grip.'

21: In. Combination with tive vSpring 201e-v -vnected elements offa mechanism, a cam shaped member/rotatably monn'tedon one of said elemente and fomcllllg 1.1163415 Oglnltmg andterrnmating inthe otheronelof said ele- "for, cati-sing the forcent saidreeoil to rotate combination -vvith l tivo resiliently connectedv bodies, av cylindricaly drinn` eccentrically"p ivotedl on one` ofv saidk bodies, and conne tingnieans originating and terminating/inthe other one of said bodies adapted to have africti'onalgrip.,onsaiddrnm When said lbodies kare imder recoil from aV relative said cam shanedinember aga-inst said lremotionin a certain direction fori'causing the force4V of,v said recoil to 'rotate said drinn` eeeiestsarl" feti'oeel grip.

23. VIn ahsnnbber, the combination with two relatively movable elements, cfa cam shaped member `inonint'edV forrotation on one of'said elements,fandfpoiver,transmissionmeans having itsfterminals'at the lother one of said elenientsfand adapted tor grip said cam shaped memberl vvhen said bodies 'move relatively yto one another in one direction .534- i u l relative y movable elements, cfa cam shaped member rotatable about a fixed point on' one ceI tion'ab'outafixedpoint on 'one of saidl eleof 'said' elements, and power transmission means having" its terminalsV secured tothe othenone of said elements and 'adapted to frictivonallyy grip said' cam shaped member.l

when tli'efrelative motion of said elements is in one direction.

25.V In a snnbber,the combination with twoY relftively movable elements, Ohta cylindrical driim eccen'tijically pivoted on'one of said eleirie ts',l and( 'a'flgexible ,member having its terminals/'at the other one of said elements and Yadapted too* p saidV drum when the relatiyef'niotion ofsaid element-s is in'one diadapted to circnmferentially grip saiddrum When said elements are under recoil from the direct action of saidfsprin'g;

'2.7. :In a s11nbber,the combination With two resiliently connected "'elements, of ay cylindrical 'drum eccentrically mounted for rotaments, landa flexible memberfhaving its ends i 'dfto'the'other one'fofsaid elements and adapted Yto be 1cirninfer'eiiti'al'ly in vfrictional Contact with" said idriim'vvhen said. elements la snnbber, ,th` combnation with tion ofsa'id 'elements is in one the slack of 2 Ina snubber, the combination with two Y elements adapted to beslack or tant accord-y ing as the relative motion of said elements is in Yone or in theoppositer direction, and means for taking up the slack of said transmission means by motion of said member.

29.` In'y a snnbber, the combination with tivo Vrelatively movable elements, of a .mem-

ber rotatably mounted on one of .said elements, a flexible connection with said member' havingits terminals at the other one of said elements adapted to be slack or taut according` as the relative motion of said elements is in one or in the opposite direction, and springactnated means for taking up the slack of said flexible means.

30. In combination With two relatively7 movable bodies, a cam shapedmember rot-atable about a fixed point onfone of said bodies, flexible connecting means With said cam sha )ed member having its terminals secured tot e other one of said bodies adapted to be slackor tant'according as the relative m0- tion of said bodies is'in one or in the 0pposite directiomand means for taking up the slack'of said flexible connecting vmeans by causing said cam shaped member to rotate.

3l. In combination With two relatively movable elements of a mechanism, acylindrical drum eccentrically mounted' for rotation on one'of said elements, a flexible member connecting' said drum to theV other one of said elements'a'nd having its ends secured thereto','s`aid`flexible member being;` adapted to be slack or tant accordingas the relative mosite direction,and spring' actuated means for rotatingsaid drumand causing' it to take up said flexible member. i 32. In combination with two relatively movable bodies, means connecting said bodies and comprising a'rinid member movablyattached toone oi' said bodies and a flexible connection with said rigid member having its terminals at the other one of said bodies adapted to be slack or taut according` as the relative motion of' said' bodies is in one or inthe opposite direction, means for taking up the slackof said flexible connection causingsaid rigid member to move, and means for' limiting),l the motionojf said rigid member.V .A i

41331"'In a device for controlling relative motion of'two bodies, a cylindrical drum eccentrically mounted for rotation on one of said bodies, meafnslimitingsaid rotation in one direction,v and a flexible connection With said or in the oppo- 35,*A mechanism Vtive motion of two elements comprising a of said bodies made operativeby theielative motion ot saidbodies `in one direction.

84, A'ine'chanism tor snubbing; the relative motion of two'elements comprising arrigid meinbermovably attached toone ot'said elen ments,rf1eXible meanshaving its terminalsat thenother one otsaidelemeiits adapted to "have a slidingv gripV on Said rigid' member when the relative motion of said `bodies isin one direction,A and means tor controliing the strength ot said grip.

' for snubbing vtnerelarigidv member rotatablyfmounted on one ot lsaid elementsiexible means having' its tei'- B6. In combination w'th 'two `relatively` movable bodies, a cylindrical drum eccentriy'for controlling tlie strength of said grip.

cally pivcted on'one oit said bodies, exible means having' its terminals secured tothe other one'o" saidbo'dies adaptedto have a' grip on said drumk when .the relative motion ot said bodies is inV one direction, andmeans 37. In Va snubber, lthe ,combination` with: two "relatively movable elements, lO a rigit member movablyattached to one oi' said ele` ble of relative Ymotion subject to the interacments, a'bralring vdevice for said rigid'memberoperative ywhen the relative motion'ot said elements isin'one direction originating and terminating' in the other one 'of said-ele'- ineiits,'andmeans for controlling said brakf ingl device.V

38. In V av sniibber, the combination with two relatively movable elements; of meinjf ber rotatably mounted 'on one otsaidjwele ments, means tor braking thevrotationot.

said member made operative' by tlie'iel'ative motion ot said elements in one direction orig'n inatiiigl Vand terminating in the other `one of saidy elemeiits,'and means tor controlling; said braking means. ,i Y

39-In .a snubber, the combinationwitlr two relatively movable elements, of a cani shaped member rotatably mountedv on kone Y otV said elements, Vflexible means having its terminals at the other'oiie o'said elements i yadapted to-bralie tlie rotation ot said' cam l ible means.'

y shaped'member when the relative motion or' said elements is in one direction, and means ,for controlling thebraking'effect of said ilex- 40.' In combination with vtwo relatively movable bodies, a Cain shaped member rotatc means having its terminals at'the other one of said bodies adapted to frictionally gripv saidcam shaped memberwhen the relative ably mounted on one of said bodies, iiexible motion of said bodies is in one direction, and means 'for controlling the riction'between etfsaid vfrictional contact. Y

th vtwo relatively Y ii. in, Combination i 'with evo freiaiiveiy movable bodies, a cylindrical drum'eccentrically pivoted on one of'said bodies, means `originating andfterminating at the `other' one et said bodies adaptedito brake vthe rotation of said drum when therrelativeimot'ion of saidv bodies vone direction, andlineans for controlling'said braking means.

42. Ina snubber, the combination withtwo relatively movable elements,fof a cylindrical drum eccentrically mounted for rotation on one of said elements,` .ilexible means having its Aterminals at the other oneV of said eleii'ieii'ts-aclapted to be circumferentially in frictional vcontact.withsaid drum when the relative motion oit' said elements is `in one direction,fand means for varying the; extent 343. In combination wi movable bodies subject to the interaction ot a torce, amember'movably 'mounted on one et saidbodies, means connecting the other oneiof said bodies witlrsaid member for transmitting said force theretoin onedirection at points where said torce applies `opposing 1 torques of different intensity to said member,

andmeans for varying tlie dierentialaCtiOn of said force at said'points."v g.

4e. In combination lwith two bodies capation ot aifor'ce, a member rotatably mounted transmitting said force theretoinoiie-direction at 'points Where it ,isj adaptedto. apply opposite torques of different magnitudefoi said member, and means for varying the difterence lbetween said oppositetorques.

in `combination with two bodies :capable of relative motion subjectto the interaction oi a torce, :,tcam'shap'ed member pivoted onone oi' said bodies, flexibleine'ans connect'- ing4 the other one said bodies to said cam shaped member yfor' transmitting said force thereto inone direction at points where itis [adapted toapplyopposite. torques'of dii'erent magnitude to said cam 'shaped member, Y

and means for varying the difference between said oppositetorques 'byfchanging the position of saidv cam shaped'member relatively to its pivots. Y

46. In Vcombination with two bodies capab lel ot' relative motion subject to the interac- Y tion of a force, a cylindrical driim pivotally mounted on one of said bodies, flexible means connecting theother lone of? said bodies to saidjdrnm fortransmitting said force thereto V inone direction at `points where it is adapted to apply opposite torques of different magl. In` combination With twovv relatively nitride to said drum, and means forvarying v the di'ferenc'ebetween said torques by chang- 4ingij the eccentricity of said drum. Y

movable bodies subject to the interaction of a force, a member movably connected to one of said bodies, and meansv for transmitting said force to said member at points'where the actions ofv said force on said member are opposing` one another, thereby producing a differential action, the points of application of saidforce varying as said member moves and conforming to predetermined variations of said differential action.

48. In combination with two resiliently f connected bodies, a member movably connected to one of said bodies, and means for transmitting the torce of recoil from the resilient action between said bodies to said member vat points where the actions of said force on 'said member are opposing one another,

l of said bodies, and means for transmitting` Y said. force to said member at points where said force applies opposing torques thereto, thereby producingl a diiierential torque, the points of application of said force varying as said member rotates andv conforming to predetermined variations of said dierential torque.

50. In combination with two relatively movable bodies subject to the interaction of a force, a cylindrical drum eccentrically pivoted on one' of said bodies, and ,means for transmitting said force to said drum at points where said force applies opposing torques thereto, thereby producing' a dierential torque, the eccentricity of said drum con` forming to predetermined Variations of said diiferential torque.

5L In combination with. two relativelyy movable bodies subject to the interaction of a force, av cam shaped member rotatably mounted on one of said bodies, and means for l transmitting said force to said cam shaped member at points where said force applies opposing torques thereto, thereby producing a differential torque, the shape of said cam shaped member conforming to predetermined variations of said differential torque.

PETER NICHOLAS PETERS. 

